Apparatus for selectively detonating a



United States Patent Ofitice 3,125,964 AEPARATUS FGR SELECTHVELY DETDNATING A PLURAMTY (EF EXPLOSIVE CHARGE MEAN John D. La Rue, Andrews, Tern, assignor, by mesne assignments, to Jersey Product on Research Company, Tuisa, Okla, a corporation of Delaware Filed June 18, 1962, Ser. No. 203,256 5 Claims. (Cl. 166-55.5)

This invention relates to detonation of explosive charges at a remote location, and more particularly to well perforating apparatus for selectively firing a multiplicity of electrically detonable perforating means individually.

In connection with the preforation of well casings for the purpose of opening up fluid communication between the bore of a well and earth formations therearound, it is the usual practice to use a perforating gun having a multiplicity of explosive charges positioned therealong which are interconnected by a line explosive, such as Primacord, for the purpose of detonating the explosive charges. The Primacord is detonated by an electrically detonable squib disposed in the housing of the perforating gun. In is manifest that substantially simultaneous detonation of the line explosive and the explosive perforating charges releases a tremendous amount of energy into the borehole. oftentimes this energy is so intense as to severely damage the well casing. Manifestly, it is desirable to eliminate the use of line explosive and to individually detonate the perforating means.

Furthermore, a great deal of pin-point perforating is currently being done in certain areas, such as in West Texas. In the pin-point technique well casing is per forated opposite potential oil zones with only one or two shots. More often than not these oil zones are widely spaced to 30 feet). Since the zones perforated are usually further apart than the length of the perforating gun, current practice requires that the perforating gun be pulled from the hole and reloaded after each zone is perforated even if only one shot was required to perforate the zone. Manifestly, it is desirable to eliminate as many as possible of the trips in and out of the hole required to load the perforating gun.

In accordance with the present invention, a plurality of electrically detonable explosive charge means located at a remote location, such as in a well bore, are connected to a pair of electrical conductors extending from an operating location to the remote location by means of a stepping switch and a unidirectional conduction means such as a semiconductor diode. The stepping switch is provided with an actuating winding connected between the electrical leads by a second unidirectional conduction means poled oppositely to the first unidirectional conduction means so as to conduct electricity when the voltage between the leads is opposite to that required for conduction through the first unidirectional conduction means. The stepping switch is arranged so that the diode is individually connected to the explosive charge perforating means to form a series circuit between the electrical conductors and is successively connected to the perforating means upon successive energizations of the actuating winding. Thus, by sequentially reversing the polarity of voltage applied to the electrical conductors at the operating location, the plurality of explosive perforating means can be individually detonated in sequence.

Objects and features of the invention not apparent from the above discussion will become evident upon consideration of the following description of the invention taken in connection with the accompanying drawing, wherein:

FIG. 1 is a schematic diagram of a well installation and apparatus in accordance with the invention illustrat- 3,126,9h4 Patented Mar. 31, 1964 ing the perforation of a well in accordance with the invention; and

FIG. 2 is an electrical schematic diagram illustrating the electrical interconnection of the perforating and control apparatus of FIG. 1.

With reference now to FIG. 1, there is shown a borehole 3 extending from the earths surface 1 to a productive subsurface formation 4. The well is shown as having a casing 8 bonded to the surrounding earth formation by a cement sheath 7 in the usual manner. A perforating gun 18 is suspended in the well bore from a pulley 25 at the earths surface by the usual perforating gun cable 9. No well head apparatus is shown in FIG. 1, but it is to be understood that a usual type of well head apparatus may be employed having a lubricator through which the cable may be run. The well logging cable 9 should have at least two electrical conductors. If the cable is shielded, the shield may serve as one of the conductors. The cable 9 is shown as being connected to a winch 27 on which it may be wound according to usual practice. The electrical conductors are connected to a direct current voltage source 31 through a selector switch 2's, the combined function of which is to energize the conductors with a voltage of controllable polarity.

Housed within the elongated perforating gun housing it) are a plurality of explosive perforating means 17, 19, 21, and 23, here shown as being explosive jet charges, adapted to be detonated by caps 17a, Ma, Ma, and 23a, respectively. Also housed within the elongated housing in are a plurality of semiconductor diodes 11, 12, and i3, and a stepping switch 15.

With reference now to FIG. 2, the selector switch 29 is shown as being a conventional double-pole, doublethrow reversing switch, the knife terminals 33 and 35 of which are respectively connected to the positive and negative terminals of direct current source 31. The perforating gun cable 9 is provided with a pair of electrical conductors 45 and 47; conductor 45 is connected to switch terminals 37 and 43, and conductor 47 is connected to switch terminals 41 and 39. Thus, when the switch blades are thrown to the right as shown, conductor 47 is positive with respect to conductor 45, and when the switch blades are thrown to the left, the conductor 45 is positive with respect to conductor 47.

Stepping switch 15 may be any of a number of types of stepping switches wherein a multiplicity of electrical circuits are individually completed in sequence upon successive energizations of an actuating coil thereof. The simple type of stepping switch illustrated in the drawings includes a plurality of contacts 61, 63, 65, and 67 individually connected to the caps 17a, 19a, 22a, and 23a. The caps are all electrically connected to conductor 47. An electrical terminal 69 is connected to the movable switch arm which is mounted on a wheel 59 having serrations on the periphery thereof. As wheel 59 rotates clockwise, switch arm on sequentially contacts terminals 61, 63, 65, and 67 to complete a circuit therewith to terminal 6. Switch armature 51 is connected to an actuating arm 53 having a pivoted dog 57 thereon which is adapted to engage the serrations in wheel 59 so as to rotate the wheel clockwise, as viewed, when the actuating arm 53 is moved vertically. The dog 57 is adapted to rotate into recess 55 in arm 53 until the arm reaches a lowermost position thereof whereat the dog will fall into the position viewed so as to engage the next serration in wheel 59. The armature 51 is provided with an actuating winding 49 which is connected between conductors 45 and 47 by'unidirectional conduction means such as semiconductor diode 11. The diode preferably is a conventional type of selenium or silicon semiconductive material having a high peak inverse voltage rating. The actuating winding 49 is Wound so that the armature will be raised, as viewed,

when current flows from conductor 45 to conductor 47 through the actuating winding and diode 11. Diode 13 is connected across the actuating winding to short circuit any voltage that may be induced therein when current ceases flowing therethrough. Diode 13 is poled oppositely to diode 11. A third diode 12 is connected between terminal 69 and conductor 45. This diode is also poled oppositely to diode 11 so that current will fiow therethrough only when conductor 47 is positive with respect to conductor 45.

Let it be assumed that the apparatus has been lowered into a Well bore as illustrated in FIG. 1, and that the switch arm 60 is contacting terminal 61 as illustrated in FIG. 2, with the knife blades of selector switch 29 in the position shown so that conductors 45 and 57 are not electrically energized. When the perforating gun is at the desired level in the well bore, the knife blades are thrown to the right so that the knife blades engage terminals 41 and 43. Current will flow through the cap 23a, stepping switch 15, and diode 12 to detonate explosive charge 23. Switch 29 is then thrown to the opposite position so that the knife blades engage terminals 37 and 39. Current Will flow through actuating winding 4% and diode 11 to rotate wheel 59 so that the switch arm as contacts terminal 63. Reversing the selector switch 29 will result in the detonation of explosive perforating charge 21. Thus, successive reversals of the polarity of the voltages applied to leads 45 and 47 will alternately move the switch arm 60 to the next electrical contact to place another explosive charge in series circuit relationship with diode 12 and detonate the charge.

Manifestly, more than one explosive charge can be detonated at one time by connecting the caps thereof in parallel. Furthermore, other types of explosive perforating charges than explosive jet charges can be used, such as the type utilizing solid bullets.

The invention is not necessarily to be restricted to the specific structural details, arrangement of parts, or circuit connections herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of the invention.

The objects and features of the invention having been completely described, What I wish to claim is:

1. Apparatus for selectively detonating from an operating location a plurality of electrically detonable explosive charge means located at a remote location, said apparatus comprising:

first and second electrically conductive leads extending from said operating location to said remote location;

first unidirectional conduction means connected to said first lead;

a stepping switch at said remote location including an actuating winding and switching means for individually connecting the explosive charge means between said first unidirectional conduction means and said second electrical lead in sequence, responsive to suecessive energizations of said actuating winding;

said first unidirectional conduction means being poled so that current will flow therethrough when said second lead is positive relative to said first lead;

second unidirectional conduction means connecting said actuating winding between said first and second leads, poled so that electrical current will flow therethrough when said first lead is positive with respect to said second lead; and

means at said operating location connected to said first and second leads for applying direct current voltages of opposite polarities to said first and second leads in alternation.

2. Apparatus for selectively detonating from an operating location a plurality of electrically detonable explosive charge means located at a remote location, said apparatus comprising:

first and second electrically conductive leads extending from said operating location to said remote location;

first unidirectional conduction means connected to said first lead;

a stepping switch at said remote location including an actuating winding and switching means for individually connecting explosive charge means between said first unidirectional conduction means and said second electrical lead in sequence, responsive to suecessive energizations of said actuating winding;

said first unidirectional conduction means being poled so that current will flow therethrough when said second lead is positive relative to said first lead;

second unidirectional conduction means connecting said actuating winding between said first and second leads, poled so that electrical current will flow therethrough when said first lead is positive with respect to said second lead;

means at said operating location connected to said first and second leads for applying direct current voltages of opposite polarities to said first and second leads in alternation; and

third unidirectional conduction means connected across said actuating winding oppositely poled with respect to said second unidirectional conduction means.

3. Apparatus for successively perforating a well pipe at a plurality of locations therealong, comprising:

an elongated housing;

a plurality of electrically detonable explosive perforating means longitudinally spaced apart in said housing for perforating laterally of the longitudinal axis of said housing;

a cable connected to the upper end of said housing for suspending said housing in a well, said cable including first and second electrical conductors extending from the Well head end of said cable to said housing, said first conductor being connected to each of said explosive perforating means;

stepping switch means in said housing, including an actuating winding, a plurality of electrical contacts adapted to be individually electrically connected to individual ones of said perforating means, an electrical terminal, and means for electrically connecting said terminal to each of said contacts individually and in succession, responsive to successive electrical energizations of said actuating winding;

first unidirectional conduction means connecting said terminal to said second conductor;

second unidirectional conduction means connecting said actuating winding between said first and second conductors, poled oppositely to said first conductor to conduct current when the voltage between said conductors is opposite to that required for electrical conduction through said first unidirectional conduction means;

third unidirectional conduction means connected across said Winding oppositely poled relative to said second unidirectional conduction means to oppose current conduction when current is flowing through said second unidirectional conduction means and through said winding; and

means connected to the well head end of said first and second conductors for applying direct current voltage therebetween of controllable polarity.

4. Apparatus for successively perforating a well pipe at a plurality of locations therealong, comprising:

an elongated housing;

a plurality of electrically detonable explosive perforating means longitudinally spaced apart in said housing for perforating laterally of the longitudinal axis of said housing;

a cable connected to the upper end of said housing for suspending said housing in a well, said cable including first and second electrical conductors extending from the well head end of said cable to said housing, said first conductor being connected to each of said explosive perforating means;

stepping switch means in said housing including an actuating winding, a plurality of electrical contacts individually electrically connected to individual ones of said perforating means, an electrical terminal, and means for electrically connecting said terminal to each of said contacts individually and in succession, responsive to successive electrical energizations of said actuating winding;

first unidirectional conduction means connecting said terminal to said second conductor;

second unidirectional conduction means connecting said actuating winding between said first and second conductors, poled oppositely to said first conductor to conduct current when the voltage between said conductors is opposite to that required for electrical conduction through said first unidirectional conduction means; and

means connected to the well head end of said first and second conductors for applying direct current voltage therebetween of controllable polarity.

5. Apparatus for successively perforating a well pipe at a plurality of locations therealong, comprising:

an elongated housing;

a plurality of electrically detonable explosive perforating means longitudinally spaced apart in said housing for perforating laterally of the longitudinal axis of said housing;

a cable connected to the upper end of said housing for suspending said housing in a well, said cable including first and second electrical conductors extending from the well head end of said cable to said housing, said first conductor being connected to each of said explosive perforating means;

first unidirectional conduction means connected to said first conductor;

stepping switch means having an actuating winding for individually connecting said explosive perforating means between said first unidirectional conduction means and said second electrical conductor in sequence, responsive to successive energizations of said actuating winding;

second unidirectional conduction means connecting said actuating winding between said first and second electrical conductors poled oppositely to said first unidirectional conduction means so as to conduct electrical current when the voltage between said conductors is opposite to that required for electrical conduction through said first unidirectional conduction means; and

means connected to the well head end of said first and second electrical conductors for applying direct current voltage therebetween of controllable polarity.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,786 Turechek July 13, 1954 2,917,280 Castel Dec. 15, 1959 3,010,396 Coleman Nov. 28, 1961 

1. APPARATUS FOR SELECTIVELY DETONATING FROM AN OPERATING LOCATION A PLURALITY OF ELECTRICALLY DETONABLE EXPLOSIVE CHARGE MEANS LOCATED AT A REMOTE LOCATION, SAID APPARATUS COMPRISING: FIRST AND SECOND ELECTRICALLY CONDUCTIVE LEADS EXTENDING FROM SAID OPERATING LOCATION TO SAID REMOTE LOCATION; FIRST UNIDIRECTIONAL CONDUCTION MEANS CONNECTED TO SAID FIRST LEAD; A STEPPING SWITCH AT SAID REMOTE LOCATION INCLUDING AN ACTUATING WINDING AND SWITCHING MEANS FOR INDIVIDUALLY CONNECTING THE EXPLOSIVE CHARGE MEANS BETWEEN SAID FIRST UNIDIRECTIONAL CONDUCTION MEANS AND SAID SECOND ELECTRICAL LEAD IN SEQUENCE, RESPONSIVE TO SUCCESSIVE ENERGIZATIONS OF SAID ACTUATING WINDING; SAID FIRST UNIDIRECTIONAL CONDUCTION MEANS BEING POLED SO THAT CURRENT WILL FLOW THERETHROUGH WHEN SAID SECOND LEAD IS POSITIVE RELATIVE TO SAID FIRST LEAD; SECOND UNIDIRECTIONAL CONDUCTION MEANS CONNECTING SAID ACTUATING WINDING BETWEEN SAID FIRST AND SECOND LEADS, POLED SO THAT ELECTRICAL CURRENT WILL FLOW THERETHROUGH WHEN SAID FIRST LEAD IS POSITIVE WITH RESPECT TO SAID SECOND LEAD; AND MEANS AT SAID OPERATING LOCATION CONNECTED TO SAID FIRST AND SECOND LEADS FOR APPLYING DIRECT CURRENT VOLTAGES OF OPPOSITE POLARITIES TO SAID FIRST AND SECOND LEADS IN ALTERNATION. 